What Limitations Are There on the Breadth of Otherwise Novel and Non-Obvious Patent Claims?

Clients are often surprised and perplexed at the breadth of patent claims their competitors obtain because they seem to go well beyond the descriptions and examples in their patents.  In our experience, patent lawsuits typically involve situations where the accused product is not specifically described in the specification of the asserted patent yet the patent has broad claims that encompass the accused product.

This frequent situation occurs because the courts have long held that the claims of a patent are not necessarily limited to the embodiments described in the specification.  However, this legal doctrine is in tension with another doctrine: patent applicants may only claim their inventions as broadly as the prior art and their disclosures will allow.  Given this tension, how do you determine when patent claims are permissibly broader than the specification embodiments or impermissibly broad in view of their disclosures?

There are two key requirements of the Patent Statute that potentially serve as a check against overly broad patent claims regardless of whether they are novel and non-obvious: The written description requirement and the enablement requirement.  In many cases, compliance with these requirements (especially the enablement requirement) is not addressed during prosecution of the patent application in the Patent Office.  In addition, the scope of the claims as determined by the court will impact whether the written description or enablement requirements are met, and the tendency of many patent holders to blindly seek claim constructions that are as broad as possible may leave them vulnerable to attack.

The Written Description Requirement

In general, and especially in the so-called “predictable arts” (e.g., mechanical inventions), the written description requirement does not provide much protection against overly broad claims, at least in the United States.  The Patent Office applies a strong presumption that any claims included in the application at the time of filing satisfy the written description requirement.  Thus, it can be difficult to challenge broad claims that are in the application at the time of filing on the grounds of an insufficient written description.

The legal standard for determining compliance with the written description requirement does not provide much guidance.  The courts have held that to satisfy the written description requirement, “the patent specification must clearly allow persons of ordinary skill in the art to recognize that the inventor invented what is claimed.”  Gentry Gallery, Inc. v. Berkline Corp., 134 F.3d 1473, 1479 (Fed. Cir. 1998).  But, how does this standard relate to claim breadth?

There are a few scenarios when the written description requirement may provide a means of invalidating broad claims.  First, if a claim is broadened after the application is filed, it will not be entitled to the presumption that it satisfies the written description requirement.  In some cases in the predictable arts, courts that have invalidated broad claims under the written description have relied on statements in the patent which suggest that the scope of the invention is limited.  For example, in Gentry Gallery, the patent claims described a double reclining seat sectional sofa that included a fixed console between two reclining seats and recliner controls.  At the time the application was filed, the broadest claim mentioned locating the controls on the console.  However, the claims were broadened to allow the controls to go anywhere on the sofa.  The Court held that statements in the specification suggested that the controls should be limited to that location and that the issued patent claim violated the written description requirement.

In other cases involving chemical species or biotechnology, the written description requirement may be useful for attacking broad claims if only a limited number of species falling within the scope of the claims is disclosed.  In In re Curtis, 354 F.3d 1347 (Fed. Cir. 2004) the patent applicant obtained a patent that claimed dental floss made from polytetrafluoroethylene which included a friction reducing coating with a specific coefficient of friction range.  The applicant attempted to reissue the patent and remove the coefficient of friction range from its claims.  The original application described only one friction reducing coating, microcrystalline wax.  The Court held that a disclosure naming one species (e.g., microcrystalline wax) can only support later-filed genus claim (e.g., friction reducing coatings) if the application clearly conveys to one of skill in the art characteristics common to all species that explain how and why they make the invention operable.  As a result, the Court held that the broadened claims did not satisfy the written description requirement.

Although the written description requirement is most useful in the case of amended claims, the Patent Office’s guidelines for applying the written description requirement also specify that it is possible for original claims to violate the written description requirement for overbreadth where the claims require an essential or critical feature that is not described in the patent and which is not conventional in the art.

The Enablement Requirement

The enablement requirement is perhaps more useful than the written description requirement in attacking overly broad claims. The Patent Statute requires that a patent describe an invention such that one of ordinary skill in the art could make and use it.  The Federal Circuit Court of Appeals has also made clear that the “full scope of the claims” must be enabled.  Therefore, when patent holders assert that their claims cover embodiments that were never contemplated or described in their patents, it may be possible to invalidate the claims if it can be shown that one skilled in the art could not have practiced all of the covered embodiments.  For example, in Automotive Technologies Int’l v. BMW of North America, et al., 501 F.3d 1274 (Fed. Cir. 2007), the patent-in-suit claimed a side impact crash sensor for a vehicle.  The patent-in-suit described mechanical sensors in detail, but included a more limited discussion of electronic sensors.  The patent holder argued that because it enabled one embodiment falling within the scope of the claims, the claims were enabled and valid.  Alternatively, the patent holder argued that one skilled in the art could have supplied the missing information based on existing knowledge on the field.  However, the Court disagreed, holding that “the novel aspect of an invention must be enabled in the patent.”  Id. at 1283.  The Court also noted that the patent holder “sought to have the scope of the claims . . . include both mechanical and side impact sensors . . . but was then unable to demonstrate that the claim was fully enabled.”  Id. at 1285.

In Magsil Corp., et al. v. Hitachi Global Storage Technologies, Inc., et al., 687 F.3d 1377 (Fed. Cir. 2012), the patent holder’s claims covered a device for forming a “tri-layer tunnel junction” that included an electric insulator with a resistance that changed by “at least 10%” upon applying a “small magnitude of electromagnetic energy.” The patent holder sought and obtained a claim construction covering resistive changes of 100% or more.  However, the evidence showed that it took more than 12 years after the filing of the patent application to reach such levels.  Because the patent did not teach how to achieve resistive levels commensurate with the scope of the claims, the Federal Circuit held the claims were invalid for lack of enablement.


Compliance with the written description requirement is a question of fact, and compliance with the enablement requirement is a question of law based on underlying factual issues.  As a result, these paths to invalidating broad claims may be difficult without going through discovery and/or to trial.  Nevertheless, the foregoing cases suggest some possible strategies for dealing with overly broad claims even where the prior art does not provide a significant basis for invalidation.

Look for Amendments That Remove Important Claim Features:  Broad claims that result from claim amendments may omit features that the specification indicates are important.  Such amendments may provide a basis for a written description attack.

Think About Undisclosed Species or Embodiments Other than the Prior Art and Accused Product:  Litigants often focus on the accused product and the prior art.  However, patent holders that seek overly broad claim constructions may inadvertently cause their claims to “read on” or cover other products that are clearly not enabled or which one skilled in the art would not have believed were possessed by the inventor at the time the application was filed.   Identify these other products.

Develop the Steps Necessary to Make and Use the Undisclosed Embodiments: Once you have identified embodiments that were not disclosed in the patent but which the claims may nevertheless read on, work with your employees or experts to determine what steps would have been required to make and use those embodiments starting from the teachings of the patent-in-suit.  The steps may help you establish that the full scope of the claim is not enabled or compliant with the written description requirement.

Get a Good Expert:  Enablement and Written Description Requirement challenges will often involve a “battle of the experts.”  Make sure your expert is persuasive and credible.